The major objective of the project is to identify the host factors associated with resistance to dental caries. Adults with no history of dental caries, despite environmental challenge, are the focus for comparative studies with matched subjects with high caries activity. Separately collected salivary secretions, pellicle and plaque are examined in the two groups for factors that can modify: 1) bacterial adherence, growth, and acid production and 2) the ability of the generated acid to produce demineralization. Parameters to be examined include: a) direct antibacterial factors, such as SIgA antibody levels against specific antibodies, lactoferrin, lysozyme and lactoperoxidase (amount and antibacterial activity); b) aggregation potential; c) amount and nature of acids and bases produced in plaque, employing a recently modified system of liquid column partition chromatography. The concentration of specific phosphoproteins and cationic proteins will be compared and their protective properties assayed in in vitro systems (in collaborative studies).